Fiber optic cable finds many applications. In addition to transmitting light in a longitudinal mode, such cable also transmits light laterally. For data communications, an effort is made to minimize such lateral transmission; however, for decorative accent lighting and displays, lateral transmission is encouraged in order to provide uniform sideways lighting or "glow" over the length of the cable. An example of a fiber optic cable which enhances lateral illumination is given in Kingstone U.S. Pat. No. 5,333,228, the disclosure of which is incorporated herein by reference.
Lateral emissions from fiber optic cable are useful for area lighting and spotlighting, such as around swimming pools, walkways, signs, and for other safety and decorative accent lighting applications. In a typical such lateral emission application, one or more lengths of cable are positioned around an area or structure to be illuminated or accented, and coupled at one or both ends to receive light from a light source. Installations are frequently outdoors, involving exposure to the elements. The light source usually comprises a housing enclosing a high intensity, gas discharge lamp having an integral or separate reflector adapted to concentrate light from the lamp onto the ends of the cable fibers, and ferrule or bushing means for fixing the position of the cable relative to the lamp. A color wheel or similar movable color filter mechanism may be interposed between the lamp and the cable, for control of color of the emitted light.
Such devices suffer from certain drawbacks. The contained high intensity, gas discharge lamp is a major source of heat which must be dissipated. The problem is especially acute because reflectors of conventional light sources (see, for example, the truncated ellipsoid reflector arrangement in Awai et al. U.S. Pat. No. 5,016,152) direct the light to a focal point coincident with the ends of the fibers. Concentrating the light (and, thus, the heat) at the entrance of the fibers can distort or melt the fibers. Attempts to avoid this problem include the use of integral face plates and dichroic filtering on the reflector. To remove heat from the housing, traditional approaches include the use of fans and heat vents for circulating air (see, e.g., Awai U.S. Pat. No. 4,922,385). Unshielded and fixed vent openings, however, admit rain, backsplash, ice and snow, thereby severely curtailing available outdoor housing placement opportunities.
Traditional lamp arrangements fix the bulb to the reflector either integrally at the time of manufacture, or by epoxy or similar permanent affixation means at the time of initial assembly. Where positioning of the filament relative to a focus (viz. proximal focal point of an ellipsoid reflector) is performed, separate bench alignment apparatus is employed prior to fixation. Subsequent in-field fine adjustment or readjustment is, therefore, rendered difficult. Fixing of the cable relative to the housing is conventionally accomplished using ferrules whose designs involve use of multiple screws, dowels and brackets to mount the cable tightly to the ferrule, making on-site installation awkward, tedious and time-consuming.
Known color management schemes employ pluralities of dichroic glass filters mounted on a movable platform for selective insertion between the lamp and the cable fiber ends. The usual arrangement employs a color wheel under stepper motor control, an example of which is shown in Hwang U.S. Pat. No. 5,184,253. Epoxy or similar means is used to permanently mount the filters perimetrically over apertures in the color wheel. Alternatively, the filters may be removably clamped between opposing framing elements joined by screws or other removable fasteners. Filter exchange and/or replacement is, thus, prevented or, at least, rendered difficult.